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posted by  PoorLamb on 7/22/2008 2:05:47 PM  |  status: Live  

Molar Solubility (WILL RATE LIFESAVER)

Course Textbook Chapter Problem
General Chemistry Chemistry: The Central Science (10th) by Brown, Lemay, Bursten 16&17 N/A
Question Details:
Find the molar solubility of Cu(OH)2 (Ksp=2.2*10-20).

a) 1.8*10-4 M
b) 3.6*10-5 M
c) 1.8*10-6 M
d) 1.8*10-7 M
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posted by CHEMNATION! on 7/22/2008 7:51:31 PM  |  status: Live
Asker's Rating: Lifesaver   
Response Details:
Cu(OH)2 <---> Cu2+ + 2OH-
 
When the solid dissolbes, let x equal the molar solubility.  This means that x moles per liter of the Cu2+ form and 2x moles per liter of OH- form.
 
Ksp = [Cu2+][OH-]2
Ksp = (x)(2x)2 = 4x3
2.2E-20 =  4x3
(2.2E-20 )/4 =  x3
Sorry, I do not have my calculator.  Take the cubed root of the result on the left and that will be your answer.
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